Method of ctjttihg gear teeth



O. G. SIMMONS 'ME'THOD OF CUTTING GEAR TEETH March 31, 1931.

' Original Filed March 24, 1927 4 Sheets-Sheet @Zwv/r mwmwaj ATTORNEYS March 31, 1931.

o. GFSIM MONS METHOD OF CUTTING GEAR TEETH Original Filed March 24, 1927 4 Sheets-Sheet 2 flux ATTORNEYS March 31, 1931. Q, SlMMQNS Re. 18,021

METHO'D OF CUTTING GEAR TEETH 4 Sheets-Sheet {5 Original Filea March 2'4, 192'? INVENTOR I MM, BY

ATTORNEYS March 31, 1931. o. G. SIMMONS Re. 18,02l

' METHOD OF CUTTING GEAR TEETH Original Filed March 24, 1'92? 4 Sheets-Sheet 4 INVENTQ BY aw $Mm AZM'MWVHZ ATTORNEY 5 Reiesued Mar. 31, 1931 PATENT OFFICE OLIVER G. SIMMONS, 01 LAKEWOOD, OHIO METHOD OF CUTTING GEAR TEETH Originallo. 1,765,385, dated June 24, 1830, Serial No. 178,021, filed March 24, 1927. Application for reissue filed September. 10,

This invention relates to a method of cutting gear teeth. In a helical gear the teeth are disposed at an angle with respect to the axis, more commonly though incorrectly 5 called spiral gears in the shop and referred to v by others as gears with twisted teeth. It is Well understood by engineers, however, that the teeth arearranged on the curve of the helix, for the reason the teeth are cut in a cylindrical body in which the lead of advance of the teeth for practical commercial purposes is made uniform. In a spur gear the teeth are straight. These gears are'intended to translate motion from one shaft to another, all of which is well understood in the art.

Various methods have been practiced commercially in cutting the teeth of helical gears, some of which may be referred to briefly.

29 The oldest in point of time is probably the milling machine method by which the index head of said machine is geared to givethe proper rotational movement to the work with respect to the longitudinal travel of the table slide, a rotary form cutter being used and caused to pass through the work and after cutting one tooth, indexing to the next and so on.

The next earliest is probably that of Hugo Bilgram, patent dated August 21, 1900, No. 656,166, in which a reciprocating tool having the form of a truncated V and operating when in contact with the teeth of a spur or helical gear blank on the principle described as the principle of evolution. The truncated V-shaped tool it Wlll berealized. is the single tooth of a rack.

The next in point of time probably is that of the hobbing method by which a hob is caused to pass across the face of a spur or helical gear blank to produce the gears desired.

The next development in point of time appears to reside in the shaping method in which a gear-shaped cutter having its teeth twisted to correspond to the angle of helix of the helical teeth adapted to be cut in the blank is reciprocated in the direction of its axis across the face of the blank, the axis of the cutter being in a fixed position with reunderstand by the Fellows 1930. Serial No. 481,041.

spect to the axis of the blank, the axes of cutter and blank being in a plane. The cutter is brought into cutting contact with the blank to the fixed position referred to, and the cutter and blank rotate slowly with a velocity corresponding to a movement of feed, and as v the cutter is reciprocated, it has in addition to the rotary feed movement referred to, a rapid rotary movement in one direction corresponding to the twist of the teeth of the cutter during the cutting stroke and a rapid rotary movement in the opposite direction corresponding to the twist of the teeth on the other motion, which is that of returning the cutter to the terminus of stroke while out of contact with the work preparatory to another cutting stroke.

In the method just described the axes of the cutter and work are in the same plane as referred to and this plane is fixed. It will be observed that due to the twist of the teeth of the cutter, the cutter has limited utility 1n that it can be used only for the helical gear having a-helical angle corresponding to the helical angle of the cutter.

Machines 0 erating on the method just described have een commercially developed I Gear Shaper Company, under patent to Edwin R. Fellows, and by the Farrel Foundry & Machine Company, under patent to W. E. Sykes.

The present invention has for an object to provide a method of generating, with a standard straight tooth gear shaper cutter, gears with helical teeth disposed at an Y helix angle and further to generate helicoi tooth faces such that all gears cut by the same cutter, or any other straight tooth gear shaper cutter conjugate to the same rack, will mesh properly with each other.

A vide a method of generating spur, or straight tooth gears with a straight tooth gear shaped 'cutter by rotating a gear shaped cutter and reciprocating the cutter across the face of a gear blank rotating in intermeshing relation with said cutter, and simultaneously tangentially moving the cutter and blank closer together by relative movement along a line tangential to a pitch circle of the butter.

further object of the invention is to pro- I tinuously rotatin together and of continuing t blan I as which lessens.

shaped cutter is non-effective, thatis,

'and'at the beginning of this Y is preferably givenan additional movement straight tooth gears with a gear shaper cutter by which t e cutter has true action on the curves of the tooth generated on the enerating aces being gear blank during the feed of the cutter.

A further ob'ect is to provide a method e mechanical difiiculties in the cuttin of gears and bywhich gears may be 'cut. wit 1 greater accuracy.

, The apparatus for practicing my invention utilizes a gear sha ed cutter in which the teeth are not twisted to the angle of helix correspondin to the helical angle of the teeth of the bl of the gear shaped cutter utilizable in the apparatus in the practice ofmy invention resides in the fact that a standard commercial straight tooth cutter, as distinguished from a twisted tooth cutter, of a normal itch correspondin to the normal pitch of t e helical gear maydm used disregarding entirely the elical angle of the helical gear.- A

ear therefore in the practice my mvention of a given pitch may be used ,to cut the teeth of any helical gear of a 'ven normal pitch. The normal pitch of te helical gear therefore is the determining factor in the practice of my invention in the utilization of'a given pitch cutter and not the helical angle of the twisted teeth of the cutter referred to as being utilized in the Sykes or the Fellows patents and commercial practices of same.

My present-invention resides broadly in the movements-of a spur gear shaped cutter conin one direction and reciprocating across 1; e face of the gear blank or work, one stroke of which reciprocating movement is in effect a cutting stroke in cutting contact with the work, while the other stroke non-cutting, it being a return of the cutter to the original osition, stroke, t e cutter to withdraw it from contact withthe ear blank, to be again moved into-positionto e ect contact during the cutting stroke simultaneousl tangentially moving the cutter or gear bla to bring the cutter and gear blank closer 's movement in the same direction to -.move said cutter and k apart; the work meanwhile rotating on an axis disposed to the axis of the cutter corresponding'to the helical angle of the .teeth desired in the blank, in one aspect of my invention, and, in another as ct of my invention, the work will meanwli ile rotate on an axis parallel to the axis of the cutter to produce the straight teeth of spur gears. From the'foregoin'g it .is understood that in the practice of my method the straight teeth of a spur gear will result if the axes fi of the work spindle and cutter. spindle are to be cut. A characteristic aspect mesh with the imaginaI adjusted and secured in parallel ositions (not angular) one with the other, an that the twisted teeth of the helical or spiral gear will result if the aforesaid axes are adjusted and secured at an an le to each other. In

my) present method, t erefore, forming the su ect matter of this specification, the straight teeth in a spur gear, or the helical teeth in a spiral gear, Wlll be produced dependent upon the ad'ustment of the axis of the work spindle with respect to the axis of the cutter spindle, or vice versa.

The movements" of the cutter and Work above referred to are very easily obtained and form the subject matter of a companion application for Letters Patent for gear shaper, Serial No. 443,185, filed April 10, 1930.

The drawings accompanying this specification are for purposes of illustration only.

Referring to the drawings, Fig. 1 is a plan view of one arrangement illustrating the method to cut a helical gear, with a. schematic diagrammatic portion showing the position of the cutter in dotted lines at the beginning of the cutting operation in rack shown by dot and dash line, said Imaginary rack also meshing with the finished helical gear; and showing also the position of the cutter in mesh with said imaginary rack after it has completed' the cutting of the teeth of the helical gear referred to.

F1 2 is an end view of Fig. 1 viewed from I the F oot of the sheet, showing the position of thegear blank and the gear shaped cutter at the beginning of the cutting of the teeth.

Fig. 3 is similar to Fig. 2, except in this view the gear shaped cutter is shown as having, completed the cutting of the helical teeth i in the gear. I

' Fig. 4 is a plan view similar to Fig. 1, except that the helical gear is shown as having the two positions occupied by the cutter of Fig. 1, namely, before and after the teeth are cut. Fig. 5 is a except'that av spur gear having straight teeth is shown in two positions; at the beginning of the cutting of the teeth and after the teeth in the gear have been fully cut by the cutter.

ferring to Fig. 1, the helical gear 1 is plan'view similar to Fig. 4,

provided with the twisted teeth 2 and is adapted to rotate slowly on its axis in the direction of.the arrow 3. The teeth 2 of the ear 1 are shown in the drawings as having en out completely by means, ofth'e spur gear shaped cutter 4 whichis provided-with teeth 5. The cutter4 is known commercially as a gear shaper cutter. .The position of the cutter 4 as shown in the drawing, Fig. 1, is substantially the position of; the cutter after it has completed the cutting of the teeth 2 of the helical ar 1. In this method the rst position 0? the cutter 4 in cutting thev teeth 2 of the helical gear 1 is indicated by the numeral 4'. The cutter in this position is shown and represented by dotted lines and is assumed to be reciprocating toward and away from the observer a. required measure of distance to clear the gear 1 as illustratedin Fig. 2. The gear shaper cutter 4 .is also rotating in the direction of the arrow 6' and moving in the direction indicated by the ar-' row 7. The rotary movement 3 of the helical gear 1 and the rotary movement 6' of the gear shaped cutter 4 being of such velocity as would be obtained'if the gear 1 and cutter 4' were meshing as shown with the imaginary the imaginary rack therefore is of infinitelength and its movement in the direction of the arrow 9 is continuous.

It is obvious that I could just as readily continuously rotate and move the gear 1 in mesh with its continuously movin imaginary rack across and into and out 0 contact with the reciprocating rotating cutter as I have moved the cutter in mesh with the: rack into and out of contact with the gear' as de-- scribed. This is illustrated in the drawing Fig. 4, the gear, cutter and artsthereof being indicated by the same re erence numerals but having the exponent a attached.

It is also obvious thatI can by the method herein described dispose the axes of the cutter and blank in parallel positions, one with the other, and produce the straight teeth of spur gears. Tl'llS is illustrated in Fig. 5,

the gear, cutter and parts thereof being indi- 'cated by thesaine reference numerals but having the exponent b attached. The

straight teeth of a spur gear illustrated in Fig. 5 will result if the axes of the work s indle and cutter spindle are adjusted an .se-

- cured in parallel positions (not angular), one

, a "with the other.

By the expression secured in parallel positions, with reference to Fig. 5, I

' mean that the axes of the work and cutter said adjusted position. ments, however, as referred to, Wlll continue "spindles are perpendicular to the surface of e sheet of the drawing and are secured in The same move-' and the axis of one will approach the axis'of the other until finally the minimum measure a.

of distance between said axes is reached, the movements continuing as described, therefore, will increase the measure of distance bet-ween said axes. In this movement the axes of the work spindle and cutter spindle 4 The position of the cutter 4', as it begins to cut the teeth of the gear 1, is illustrated in Fig. 2 and it will be observed that the position of the cutter 4' is shown for purpose of illustration to the left of the gear 1, and on its lowe'rmost position of the stroke the cutter is shown in full lines and at the top of its stroke In Fig. 3 the teeth 2 of jugate to the gear shaper cutter employed in cutting them and all gears of the same helix angle cut Withstraighttooth gear shaper cutters conjugate to the same rack will mesh properly with each other.

The helicoidtooth faces of the helical gear out in accordance with the present invention are the same generically as would be cut in the methods of the prior art by a helical gear shaper cutter conjugate to the same rack as the straight tooth cutter employed in the present method.

It is quite obvious that if the helicoid tooth faces of the helical gear cut in accordance with the present invention are adapted to be used as cutting teeth, the helical gear pro-' duced by this invention could be used as the cutter to produce, bythe method of the present invention, the conjugate rack or intermeshing conjugate straight tooth gearsby simply reversing the cutter and blank, thereby producing a straight tooth, involute gear with a helical tooth gear shaper cutter.

The method of the'present invention requires less complicated machiner since the "rates of rotation of the blank an cutter are independent of the speed of the cutting stroke, while in machines for cutting gears with a helical gear shaper cutter,'the speed of'rotation of the cutter must be correlated cutter and gear being out come into tangential contact the eneration of the gear is completed, whereas y the method ordinarily er'nployed the true generating action begins'only after the cutter has been fed to a point where its pitch circle is tangent to the pitch circle of the gear being cut. i

Having thus described my claim: v

1. A. method of generating. teeth in; gear invention I no I lee

and continuing this movement to move said cutter and blank apart.

2. A method of generating teeth in a gear blank by continuously rotating a gear shaped cutter on its axis and reciprocating the cutter across the face of a gear blank continuously rotating on its axis 1n lnterlneshing relation with the cutter, the axes of the cutter and gear blank being disposed angularly with respect to each other, and simultaneously mov 7 ing the cutter and gear blank along a line tangential to the pitch circle of the cutter and continuing this movement to move said cutter and blank apart. A

'3. A method of generating teeth in a gear blank by rotating a gear shaped cutter continuously in the same direction on its axis and reciprocating the cutter across'the face of a gear blank rotating on its axis in intermeshing relation with said cutter, one stroke of the reciprocating movement being a cutting stroke with the cutter in contact with the gear blank, the other stroke being a return non-cutting stroke with the cutter out of contact with the gear blank, simultaneously tangentially moving the cutter and blank closer together and continuing this movement to move said cutter and blank apart, and maintaining the rotation of the cutter and blank during the cutting strokes at speeds correspout-ling to the speeds at which they would be driven by their conjugate rack moving tangentially of the pitch circles of the cutter and blank.

4. A method ofvcutting helical gear teeth in a gear blank by rotating 2, gear shaped cutter in one direction and reciprocating said cutter across the face of the gear blank, one stroke of such reciprocating movement being a cutting stroke with the cutterin cutting contact with the gear blank while the. other stroke is a non-cutting stroke to return the cutter to the original position and atthe beginning of which stroke the cutter is preferably given an additional movement to withdraw it from contact with the gear blank to be again moved into position to effect contact during the cutting stroke; simultaneously tangentially moving the cutter or gear blankto bring the cutter and the gear blank closer together and continuing this movement in the same direction to move sald cutter and blank apart; the gear blank meanwhile rotating on an axis disposed to the axis of the cutter corresponding to the helical angle of the teeth desired in the gear blank, the rotary motion of said cutter and said gear blank being of such velocity as would result if the'teeth of said cutter and the resultant generated teeth of the gear blank were constantly in mesh with a continuously movin imaginary rack of infinite len h.

5. Tie herein described method o generating teeth in. earblanks by continuously .rotating a gear s aped cutter on its axis and reciprocating the cutter across the face of a ear blank continuously rotating on its axis 1n intermeshing relation with said cutter, gradually moving the axes of the cutter and blank closer together, and maintaining the rotation of the cutter and blank during such movement at speeds'corresponding to the speeds at which the cutter and blank would cutter and blank along a common tangent to 7 said pitch circles at a rate corresponding to the relative movement which the cutter and gear to be generated would have if in mesh with an imaginary longitudinally moving rack common to the cutter and gear, and simultaneously reciprocating the cutter across the blank.

7. The herein described method of generating teeth in a gear blank with a gear shaped cutter which consists in moving the cutter and blank relatively to each other along a common tangent to the pitch circle 7 of the cutter and the pitch circle of the gear to be generated, from a' position in which the cutter is clear of the blank to a position 'in which said pitch circles are tangent, separating the cutter and blank by continuing said movement in the same direction, recipro cating the cutter across the blank during such movement and rotating the cutter and blank at relative speeds such that the relative linear movement corresponds to the relative movement which the cutter and gear would have if simultaneously meshing with the imaginary moving rack common to the gear and cutter.

-8. The herein described method of generating helical teeth in a gear blank with a gearshaped cutter having longitudinally straight teeth which comprises positioning the cutter with its axis at an angle to the axis of the blank corresponding to the angle of the helix of the teeth to be cut, rotating the cutter and blank in intermeshing relation, reciprocating the cutter in the direction of its axis across the face of the blank, and

imparting to the cutter and blanka relative linear movement transversely with respect to the cutter axis along the imaginary rack conjugate to the cutter and blank.

9. The-herein described method of gencrating teeth in gear blanks by rotating a gear shaped cutter on its axis and reciprocating the cutter across the face of a gear blank rotating on its axis in intermeshing relation with said cutter, gradually moving the cutter and blank closer together, and maintaining the rotation of the cutter .and blank during such movements at speeds corresponding to the speeds at which the cutter and blank would be driven by their common intermeshin con'u ate rack movin between them .2 l g g tangentially o and blank.

. 10. A method of generating teeth in a gear blank byrotating a gear shaped cutter on its axis and reciprocating the cutter across the the pitch circles of the cutter face of a gear blank, one stroke of the reciproeating movement being a cutting stroke with the cutter in contact with the gear .blank rotating on its axis in intermeshing relation with said cutter,the other stroke being 'a return non-cutting stroke with the cutter out of contact with the gear blank, simultaneously tangentially moving the cutter and blank closer together, and maintaining the rotationof the cutter and blank during the cutting strokes at speeds corresponding to the speeds at which they would be driven by their conjugate rack moving tangentiallyof the pitch circles of the cutter and blank.

11. A method of cutting helical teeth in a gear blank by rotating a gear shaped cutter in one direction and reciprocating said cut tar across the ,face of a gear blank, one'stroke of such reciprocating movement being a cuttinglstroke'with the cutter in cutting contact wit the gear blank while theother stroke of such movement is a return non-cutting stroke of the cutter to its original position, the cutter at the beginning of this last men tioned stroke preferably being given an ad- I ditional movement to withdraw it from contact with the gear blank to be again moved 'gentially moving the cutter 'or into ositiont-o efl'ectcontact therewith during t e cutting stroke, simultaneously tanear blank to bring the cutter and the gear b ank closer together, the gear blank meanwhile rotating on an'axis disposed to the axis of the cutter at an angle corrcspondingto thehelical angle of the teeth desired in the gear blank,

the rotaryimotions of saidcutter and gear blank being of such velocity, as would result if the teeth of said cutter and the resultant generated teeth of the gear-blank where constantly in mesh with a moving imaginary rack of infinite length.

'12. A method of generating teeth, in gear blanks-by rotating a gear shaped cutter in. intermeshing relation with a rotating gear blank, reciprocating the cutter across the face of the blank and moving the cutter and blank closer together by a relative movement along a line tangent to a pitch circle of the cutter and gear blank.

posedwith respect to the axis of the gear' blank.

14. A method of generating teeth in a gear blank by rotating a gear shaped cutter on its axis and. reciprocating thecutter across the face of 'a gear blank rotating on its axis in intermeshing relation with the cutter, .the

axes of the cutter and gear blank being disposed angularly with respect to each other, and simultaneously moving the cutter and gear blank closer together by relative movement along a line tangential to a pitch circle of -the cutter. I

15. A- method of generating teeth in gear blanks comprisin rotating a gear shaped cutter in intermes ing relation with a rotating gear blank, relatively reciprocating the cutter and blank transversely of theirfaces along a line angularly disposed with respect to the axis of the gear blank, and moving the cutter and gear blank closer together by relative movement along a line'tang'ent to a pitch circle of the cutter and gear blank.

16. A methodof generating-helical teeth in gear blanks comprising rotating a gearshaped cutter in intermeshing relation with a rotating gear blank, relatively reciprocating the cutter and blank transversely 'ofi their faces along a line disposed at an angle to the axis of the blankcorresponding to the angle of the helix of the'teeth to be generated thereon, and moving the cutter and gear blank closer together by relative movement along a line-tangent to a pitch circle of the cutterand gear blank.

17. A method of generating teeth in gear blanks comprising rotating a gear shaped cutter in intermeshing relation with a rotating gear blank, relatively reciprocating the cutter and blank transversely of their faces,

and moving the cutter and gear blank closer together by relative movement along a line tangent to a pitch circle ofthe'cutter and gear blankf 18. A method of generating teeth in gear blanks comprising rotating a gear shaped cutter in intermeshing relation with a rotating gear blank, relatively reciprocating the cutter and blank transverselyoftheir faces a and along the line of their axes, and simulblank closer together, and maintaining the rogear blank.

tation of the cutter and blank during such .movements at speeds correspondin to the would speeds at which the cutter and bla be driven by their common intermeshing conjugate rack moving-between them tangentially of the pitch circles of the cutter and blank.

20. A method of generating teeth in gear blanks by rotating a gear shaped cuttgr having longitudinally straight teeth in intermeshing relation with a rotating gear blank,

reciprocating the cutter across the face of the blank and moving the cutter and blank closer together by relative movement along a line tangent to the pitch circle of the cutter and 21. A method of generating teeth in gear blanks comprising rotating the gear shaped cutter having longitudinally straight teeth in intermeshing relation with a rotating gear blank, relatively reciprocating the cutter and blank transversely of their faces alon a line angularly disposed with respect to t c axis of the gear blank and moving the cutter and gear blank closer together by relative movement along a line tangent to a pitch. circle of the cutter and gear blank.

7 22. A method of generating teeth in gear blanks comprising rotating a gear shaped cutter having lon itudinally straight teeth in intermeshin re ationwith a rotating gear blank, relative y reciprocating the cutter and blank transversely of their faces, and moving the cutter and gear blank closer together by relative movement along a line tangent to a pitch circle of'the cutter and gear blank.

23. A method of generating teeth in gear blanks comprising rotating a gear shaped cutter having lon 'tudinally straight teeth in intermeshing re ation with a rotating gear blank, relatively reciprocating the cutter and blank transversely of their faces and along the line of their axes, and simultaneousl moving the axes of the cutter and gear blank closer together by relative movement alonga line tangent to a pitch circle of the cutter and gear blank.

24. A method of generating teeth in gear blanks comprisin rotating a gear shaped cutter in intermes 'ing relation with a .rotating gear blank, relatively reciprocating the. cutter and blank transversely of their faces,

. and simultaneously moving one of these 25.-A method of generating teeth in gear i blanks comprising rotating a gear shaped cutter in intermeshing relation with a rotating gear blank, the axes of the cutter and gear blank lying in parallel planes, relatively reci rocating the cutter and blank transversely 0 their faces, and simultaneously relatively moving said cutter and said gear blank laterally in paths that lie respectively in the planes of their axes to bring said cutter and gear blank closer together.

26. A method of generating teeth in gear blanks comprising rota-ting a gear shaped cutter in intermeshing relation with a rotating gear blank, the axes of said cutter and said gear blank being in parallel planes, relatively reciprocatm transversely of then faces, and simultaneously moving the cutter laterally along a path lyin in the plane of its axis to bring the cutter an gear blank closer together.

27. The method of generating teeth in gear blanks comprising rotating a gear shaped cutter in intermeshing relation with a rotating gear blank, the axes of said cutter and said lank being in parallel planes, relatively reciprocating the cutter and blank transversely of their faces along a line angularly disposed with respect to the axis of the gear blank, and simultaneously relatively moving the cutter and gear blank laterally in paths lying respectively in the said planes of their axes to bring gether.

28. A method of generating teeth in gear blanks comprising rotating a gear shaped cutter in intermeshing relation with a rotating gear blank, the axes of said cutter and said blank being in parallel planes, relatively reciprocating the cutter and blank said cutter and blank closer totransversely of their faces and along the line of their axes and simultaneously relatively moving the cutter and blank laterally in paths lying respectively their axes to bring said cutter and blank closer together.

OLIVER G. SIMMONS.

the cutter and blank in said planes of I 

